/ic/ - Artwork/Critique

>>3774125
i guess theres a misunderstanding of terms on my part, what im trying to understand is shading shapes in a way that will make them 3d and give roundness to an object. for example i can draw all kinds of body parts with cylinders and boxes but when i try to add muscles im not sure how to shade and draw them correctly to make them look like they bulge out of the object etc.
Like in pic related where rubens bulges random muscles out of the arm by just shading them in.